1. Field of the Invention
The present invention relates to a reversible thermosensitive recording medium capable of forming and erasing a color image, using the reversible thermosensitive coloring composition, by controlling thermal energy to be applied to the recording medium, and to a label and an image forming and erasing method.
2. Description of the Related Art
In recent years, reversible thermosensitive recording mediums have been paid attention in which an image information is temporarily recorded or written and when not needed, erased or eliminated. As a typical example, there is known a characteristic reversible thermosensitive recording medium, in which particles of developer such as an organic phosphoric acid compound, as shown in Patent Publications of Tokkai Hei 5-124360 and Tokkai Hei 6-210954 and so forth publications.
However, such reversible thermosensitive recording media (these reversible thermosensitive recording medium may also be described as simply xe2x80x9crecording mediumxe2x80x9d hereinafter) in conventional art are, especially in case of image forming and erasing procedures are repeated using thermal head, suffered from rubbings by the thermal head accompanied with application of heat, therefore scratches are generated on its surface, and when the scratches have been grown considerably, there is observed a drawback that images can be not formed uniformly. This phenomenon is mainly caused by a large mechanical stress which is imposed to the surface of the recording medium in accompanied with application of heat, therefore the surface of the recording medium is deteriorated, and damages in the surface become serious, thus the durability for repeated uses is decreased. Accordingly, for decreasing the generation of such scratches on the furface of the recording medium, there are previously proposed attempts for providing a protection layer onto the recording medium surface, as disclosed in Japanese Unexamined Patent Publications of Tokkai Hei 10-291371 and Tokkai Hei 10-291372. However, it is very hard to say that the sufficient durability for scratching damages can be attained by providing only a protection layer onto the surface of the recording medium surface.
In order to cope with this problem, there is known a laser recording method that is capable of recording with non-contact mode. In this recording method the mechanical pressure does not apply to the recording layer in the period when it being softened, therefore can be evaded the deterioration of the recording medium. For example Japanese Unexamined Patent Publication of Tokkai Shou 57-82088 discloses a recording method in which carbon black is included in a reversible thermosensitive recording layer or in another layer adjacent to the reversible thermosensitive recording layer of a recording medium, and this recording medium is recorded using laser light. By this recording method, non-contact mode of recording becomes possible, however in this recording method there is a shortcoming that it causes gray tone in whole images, not only in case of that carbon black is included in a reversible thermosensitive recording layer but also in case of that carbon black is included in another layer adjacent to the reversible thermosensitive recording layer of a recording medium, thus this method significantly reduces the contract of the image. And then, Japanese Unexamined Patent Publication of Tokkai Shou 64-14077 discloses a recording method in which, instead of carbon black used in aforementioned method, an infrared ray-absorbing dye is used. By this recording method, the image density is more improved than that of aforementioned method using carbon black, however the infrared ray-absorbing dye has a light absorptive characteristic for visible light wavelength range too, therefore the contrast of image is still low with this recording method.
On the other hand, in case of a reversible thermosensitive recording medium based upon a polymer material using a physical property change that can shift its transparency between clear tone and milky tone, although the contrast of the image in the recording medium is apt to reduce a coloring by the infrared ray-absorptive dye, the visibility itself of the obtained image is not considerably decreased, as shown in a disclosure by Japanese Unexamined Patent Publication of Tokkai Hei 8-118819. By contract to this, a thermosensitive reversible recording medium capable of forming and erasing a color image shows a considerable decrease of contrast which is caused by an infrared ray-absorptive dye incorporated, causing a considerable loss of the visibility. Further the repeated printing and erasing using laser beam results the degradation of the photo-thermal conversion layer, hence decreasing the durability for repeated uses.
It is hence an object of the present invention, in view of the situation of above descried prior arts, to provide a reversible thermosensitive recording medium having improved characteristics, in which the appeared color in the photo-thermal conversion layer being concealed, thereby contrast and visibility of the image formed are improved, and showing excellent durability for repeated uses. And it is other objects of the present invention to provide an image recording and erasing method, and usage using the reversible thermosensitive recording medium, and beneficial usage of the reversible thermosensitive recording medium.
Above and other objects of the present invention are achieved by a reversible thermosensitive recording medium which comprising:
(1) A reversible thermosensitive recording medium comprising an concealing layer provided between a reversible thermosensitive recording layer which is reversibly changed in its color by heat and a photo-thermal conversion layer which absorbs light with generating heat,
wherein the concealing layer has an optical characteristic that the ratio of a light absorptivity of light having 555 nm wavelength, in comparison with a light absorptivity of laser light wavelength, is 80% or less;
(2) A reversible thermosensitive recording medium according to above paragraph (1);
wherein the concealing layer has an optical characteristic that a light absorptivity of light having 555 nm wavelength, is 1.25 or more.
(3) A reversible thermosensitive recording medium according to above paragraph (1);
wherein the concealing layer has an optical characteristic that a light absorptivity of laser light, is 1 or less.
(4) A reversible thermosensitive recording medium according to above paragraph (1);
wherein the optical reflection density at background area of the reversible thermosensitive recording layer is 0.5 or less.
(5) A reversible thermosensitive recording medium according to above paragraph (1);
wherein the concealing layer has a gel fraction ratio of 30% or more.
Above and other objects of the present invention are achieved by a card having a reversible thermosensitive recording medium which comprising:
(6) A card having a reversible thermosensitive recording medium portion and an information memory portion,
wherein the reversible thermosensitive recording medium portion is a recording medium according to above paragraph (1);
(7) A card having a reversible thermosensitive recording medium portion and an information memory portion,
wherein the reversible thermosensitive recording medium portion is a recording medium according to above paragraph (1), and the information memory portion comprises at least a memory selected from magnetic memory, I C memory or optical memory;
(8) A card having a portion of a reversible thermosensitive recording medium layer, a supporting member and a magnetic recording layer, which are being superimposed in this order,
wherein the reversible thermosensitive recording medium portion is a recording medium according to above paragraph (1).
Above and other objects of the present invention are achieved by a label having a reversible thermosensitive recording medium which comprising:
(9) A reversible thermosensitive recording label having a reversible thermosensitive recording medium portion, a supporting member and an adhesive or stickness layer, which are being superimposed in this order,
wherein the reversible thermosensitive recording medium portion is a recording medium according to above paragraph (1).
Above and other objects of the present invention are achieved by a disc cartridge having on it a reversible thermosensitive recording label reversible thermosensitive recording medium which comprising:
(10) A disc cartridge having in its inside a disc which is capable of rewriting an information and has a reversible thermosensitive recording label thereon, the reversible thermosensitive recording label has a reversible thermosensitive recording medium, a supporting member and a portion of adhesive or stickness layer, which are being superimposed in this order,
wherein the reversible thermosensitive recording medium is a recording medium according to above paragraph (1).
Above and other objects of the present invention are achieved by a disc having on it a reversible thermosensitive recording label reversible thermosensitive recording medium which comprising:
(11) A disc which is capable of rewriting an information or recording an additional information and has a reversible thermosensitive recording label thereon,
wherein the reversible thermosensitive recording medium is a recording medium according to above paragraph (1); and,
(12) A disc which is capable of rewriting an information or recording an additional information and has an attached reversible thermosensitive recording label thereon.
wherein the reversible thermosensitive recording label has a reversible thermosensitive recording medium, a supporting member and a portion of adhesive or stickness layer, which are being superimposed in this order, and the reversible thermosensitive recording medium is a recording medium according to above paragraph (1).
Above and other objects of the present invention are achieved by a cassette having a reversible thermosensitive recording label which comprising:
(13) A cassette for recording tape which is capable of rewriting an information and being attached with a reversible thermosensitive recording label,
wherein the reversible thermosensitive recording label has a reversible thermosensitive recording medium, a supporting member and a portion of adhesive or stickness layer, which are being superimposed in this order, and the reversible thermosensitive recording medium is a recording medium according to above paragraph (1).
Above and other objects of the present invention are achieved by a reversible thermosensitive recording medium and an image recording, and erasing method and apparatus which comprising:
(14) A reversible thermosensitive recording medium according to above paragraph (1), comprising image which being formed by printing;
(15) An image recording and/or erasing method, wherein a reversible thermosensitive recording medium according to above paragraph (1) is used, and at least either image recording or erasing is conducted by irradiating laser light;
(16) An image recording and/or erasing method, wherein a reversible thermosensitive recording medium according to above paragraph (1) is used, and at least either image recording or erasing is conducted by irradiating, laser light having a wavelength 700 nm or more
(17) An image recording and erasing method, wherein a reversible thermosensitive recording medium according to above paragraph (1) is used, and both image recording and erasing are conducted with adjusting at least any one among applied actions of light irradiation time, amount of light emission, focussing point of irradiated light, or intensity distribution of irradiated light.
The inventors of the present invention have studied for overcoming the foregoing disadvantages and discovered that an improved reversible thermosensitive recording medium can be obtained, in which the contrast of the image is improved by defining the relationship between the light absorptivity of a light having 555 nm wavelength and the light absorptivity of a laser beam light at a concealing layer, and the durability for repeated uses is improved too by defining the gel fraction ratio for the concealing layer.
Namely, there is provided an improved reversible thermosensitive recording medium comprising a concealing layer provided between a reversible thermosensitive recording layer which is reversibly changed in its color by heat and a photo-thermal conversion layer which absorbs light with generating heat, in which formed color of the concealing layer is concealed, contrast and visibility of the image formed in the recording medium are increased, and the durability for repeated uses is improved too, when the characteristic of the concealing layer is defined so that the concealing layer has an optical characteristic what the ratio of a light absorptivity of a light having 555 nm wavelength, in comparison with a light absorptivity of a laser light, is 80% or less, and the concealing layer is defined so that it has an optical characteristics that a light absorptivity of light having 555 nm wavelength, is 1.25 or more, and a light absorptivity of laser beam light, is 1 or less, and optical reflection density at background area of the reversible thermosensitive recording layer is 0.5 or less, the resin included in the concealing layer being cross-linked and the concealing layer has a gel fraction ratio of 30% or more.
These and other objects, features and advantages of the reversible thermosensitive recording medium of the present invention will become apparent upon a consideration of the following description including the preferred embodiments of the invention taken in conjunction with the accompanying drawings.